Ethanol from biomass: A comparative overview

This work provided an overview of the ethanol production processes from sugarcane, corn and sugar beet in terms of energy indicators, carbon emissions and economic aspects. A description of the bioethanol production process for each feedstock is first presented, providing the basis for the comparative assessment. In general, best indicator values are achieved with sugarcane as feedstock, which allows the lowest requirements of fossil inputs for ethanol production. The cogeneration system of sugarcane biorefineries can provide the energy self-sufficiency to them through the burning of the main coproduct (bagasse). The coproducts of corn and sugar beet ethanol production are normally used as fertilizers or animal feed, and thus, external energy is required for those coproducts conversion usually at the expenses of fossil fuels burning. Energy consumption in the industrial phase of corn ethanol production is even higher when compared to sucrose-based ethanol, since additional steps to convert starch to glucose are required. Such higher energy use supplied by fossil sources contributes to its lowest GHG reduction potential among the biomasses, being sugarcane the most sustainable in this aspect. Average production costs for sugarcane ethanol are also more attractive: around 50-60% lower than those for corn ethanol and 20-30% lower than those for sugar beet ethanol. Although sugarcane seems to be the most advantageous biomass for ethanol production, larger subsides are provided to corn and sugar beet ethanol (especially in USA and EU), contributing to keep USA in the worldwide leadership of ethanol production, even with the less sustainable feedstock.